Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations establish it is a mutating, non-idempotent, non-destructive call; the description adds real value beyond that with cost (0.01 USDC per query), a per-session cap (max 20 queries), and the prepaid/funded-session requirement. It does not explain what happens if the session is unfunded or how the delivery receipt is used.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with the differentiator (paid per-query access) and the free alternative. The listing/pricing detail is dense but earns its place for a metered tool, with no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a payment-gated session query with no output schema, it covers cost, quota, prerequisite flow, and the free alternative competently. The missing piece is parameter semantics (k, delivery_receipt), which the schema also leaves undocumented.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is only 40% (session_id and sandbox_receipt documented), so the schema does not carry the burden. The description adds nothing about k, query, or delivery_receipt, leaving three of five parameters with no meaning anywhere — a clear gap for a paid, receipt-bearing call.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names the specific action (buy per-query access to live data listings within a prepaid session) and identifies the concrete listing (scienceorgwatch AAAS Science). It clearly reads as a paid query tool and contrasts with the free sibling data_preview, though the core verb 'query' only appears inside the sequence rather than the leading sentence.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It supplies prerequisites explicitly via the sequence data_session_open → data_session_fund → data_session_query and routes cheap exploration to data_preview ('first taste free'). It does not state explicit when-not conditions, but the prerequisite chain is clear enough to prevent misuse.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.